Calcium-dependent protein modulator will be purified to homogeneity from bovine brain and monospecific antibody against the protein will be produced in rabbits. An immunoassay (radial immunodiffusion or radioimmunological assay) will be developed and utilized as a selective, sensitive and reproducible method for quantitation of the calcium-dependent protein modulator of cyclic 3',5'-nucleotide phosphodiesterase in tissues. The assay will be examined for selectivity among closely related calcium-binding proteins as well as sensitivity and will be compared to the present enzyme-activity assay which is based on the activation of modulator-deficient cyclic 3',5'-nucleotide phosphodiesterase of bovine brain. Utilizing the developed immunoassay procedure, calcium-dependent protein modulator will be measured in cytosolic and membranous fractions of different tissues from normal and streptozoticin-diabetic rats and obese-hyperglycemic (ob/ob) mice. The immunoassay will also be used to assess the possible intracellular translocation of modulator in heart during perfusion with insulin or glucagon. Correlation between changes in modulator distribution and cyclic AMP and cylic GMP phosphodiesterase activity will be studied.